In thermally assisted magnetic/optical recording, information bits are recorded on a storage layer at elevated temperatures, and a heated area in the storage layer determines the data bit dimensions. One approach uses a planar solid immersion mirror (PSIM) lens, fabricated on a planar waveguide and a metallic nano-structure of a specific shape, called a near-field optical transducer, placed near the PSIM focus. The PSIM directs light onto the near-field transducer to form a local surface plasmon (LSP). A high electric field surrounding the near-field transducer appears, due to collective oscillations of electrons in the metal. Part of this field will tunnel into an adjacent storage medium and get absorbed, raising the temperature of the medium locally for recording. The LSP is sensitive to the shape of the near-field transducer and its location in the waveguide. The near-field transducer may be buried in a dielectric layer of low thermal dissipation. Light is absorbed in the near-field transducer, creating heat that requires a cooling mechanism for its functioning.